Circuit for supplying power, without the need for a battery, to the electronic control unit of a machine driven by an internal-combustion engine

ABSTRACT

A circuit arrangement ( 10 ) for the batteryless power supply of the electronic control of a portable machine driven by an internal combustion engine, which machine possesses a d.c. voltage generator driven by the internal combustion engine, which delivers a generated voltage dependent on the number of revolutions of the internal combustion engine, which is transferred to a rated d.c. voltage (Vcc). The circuit arrangement ( 10 ) includes a first rectifier circuit (D 1 , C 1 ), which converts the generator voltage (Ug) into an intermediate d.c. voltage (Uz), which permits the same, without booster batteries, to reliably and controllably supply the electronics of an engine-driven machine, especially in the starting phase, with the requisite rated d.c. voltage.

The present invention relates to the area of engine driven machines. Itrelates to a circuit arrangement for the batteryless power supply of theelectronic control of a machine driven by an internal combustion engineand, more particularly, to a portable machine with a rated directvoltage. The machine possesses an a.c. voltage generator driven by theinternal combustion engine which delivers a generated voltage dependentupon the revolutions per minute of the internal combustion engine. Thecircuit arrangement comprises a first rectifier switch which convertsthe generated voltage into an intermediate d.c. voltage.

BACKGROUND OF THE INVENTION

A circuit arrangement of the type referred to above is known for thearea of motor vehicle engineering from the German patent publicationDE-A1-38 41 610.

In combustion-engine machines, electrical energy is required, for theoperation of controls which typically is made available from batteriesor is generated by generators driven by the engine. The employment ofbatteries, especially in portable machines, entails an additionalexpense, particularly as the long-term storage volume is limited.Moreover, in the batteryless operation as is provided in the DE-A1-38 41610 publication for a motor vehicle, the voltage generated by the normalgenerator through the starting process does not provide sufficientenergy for operating additional controls. However, this will benecessary in the future when engines with injection valves are morecommonly used in order to actuate a valve or the like.

The applicants have designed a power supply for anelectrically-controlled chain saw which dispenses additional energy. Inthis case, however, it did prove disadvantageous that a part of theignition energy was used for the starting process so that, on account ofthe power withdrawal connected herewith, the starting behaviordeteriorated. Since, in the case of portable machines, the startingbehavior significantly affects operating comfort, such a solution is notdevoid of problems.

Thus, an objective of the invention is to provide a circuit arrangementwhich permits a reliable power supply, without the employment of boosterbatteries, which can deliver power in the starting phase with therequisite rated d.c. voltage and which, at the same time, is simple andsturdy in its construction.

SUMMARY OF THE INVENTION

According to the invention, novel circuit arrangement comprises firstmeans which are disposed in series with a first rectifier circuit andwhich generates with a low-running level of revolutions per minute, therated d.c. voltage from an intermediatate d.c. voltage by means ofcontrolled upward transformation for so long as the intermediate d.c.voltage is lower than the nominal d.c. voltage.

Through upward transformation, the first means are capable of generatingthe requisite rated d.c. voltage from the low intermediate d.c. voltageswhich, in the starting phase may constitute, for example, merely 20% ofthe rated d.c. voltage. Once the engine attains its higher idling speedit is possible to circumvent the first means to provide the rated d.c.voltage directly through speed regulation from the intermediate d.c.voltage.

According to a preferred embodiment of the invention, the first meanscomprise a switching controller connected to a switching controllerinteracting with a serially disposed inductance coil as well as a secondrectifier circuit mounted in series with the same. By means of theswitched mode of operation, the switching controller generates elevatedvoltage peaks in the inductance coil which are rectified and result inan upwardly transformed output d.c. voltage. When the rated d.c. voltageis reached at the switching controller output, the switching controllerdiscontinues its function and the intermediate d.c. voltage is able toreach the output of the circuit arrangement via the inductance coil.

In order to ensure a constant rated d.c. voltage at higher speeds, avoltage controller is fitted preferably between the first rectifiercircuit and the first means, which generates the nominal d.c. voltagefrom the intermediate d.c. voltage when, at higher numbers ofrevolutions, the intermediate d.c. voltage is higher than the nominald.c. voltage. In addition, by preference second means are provided whichbridge the switching controller when the intermediate d.c. voltage islower than the rated d.c. voltage. Hereby a power supply operating intwo stages is realized. In the starting phase, the voltage controller isbridged and the rated d.c. voltage is generated from the (lower)intermediate d.c. voltage by means of upward transformation. In thenormal operating phase the switching controller is switched off and thevoltage controller is interconnected so that the rated d.c. voltage isgenerated from the (now higher) intermediate d.c. voltage by means ofspeed regulation. Further embodiments become apparent from the dependentclaims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an electrical circuit according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The circuit arrangement (10) described in FIG. 1 shows an input for thegenerator voltage (Ug) and two outputs for the positive rated d.c.voltage (Vcc+) and the negative d.c. voltage (Vcc−). The generatorvoltage (Ug) applied to the input is first rectified and smoothed in thefirst rectifier circuit comprised of a first diode (D1) and a firstsmoothing capacitor (C1) so that, at its output, an intermediate d.c.voltage (Uz) appears.

Behind the first rectifier circuit (D1, C1) an integrated voltagecontroller (Ic1) (e.g. of the type MC7812) with the resistors (R1) and(R2) is disposed. The longitudinal process control system of the voltagecontroller (Ic1) is bridgeable by means of a break contact element (Q),to which a diode (D2) is connected in parallel. The break contactelement (Q) forms part of a relay (Re) which is located parallel to afurther capacitor (C2) at the output of the voltage controller (Ic1).The relay (Re) is selected in such a way that it actuates when thevoltage applied to it approaches the rated d.c. voltage (Vcc) or isapproximately equal to this voltage. If the intermediate d.c. voltage(Uz) (e.g. in the starting phase) is clearly lower than the rated d.c.voltage Vcc, the relay (Re) remains off. The break contact element (Q)is closed and bridges the voltage controller (Ic1). The intermediated.c. voltage (Uz) reaches a switching controller (Ic2) and an integratedvoltage supply circuit (Ic3) via the break contact element (Q). Thevoltage controller (Ic1) only becomes effective when the generatedvoltage (Ug) or the intermediate d.c. voltage (Uz) derived therefrom isso high that the relay (Re) activates and opens the break contactelement (Q). The increasing intermediate d.c. voltage (Uz) is thenregulated by the voltage controller (Ic1) to the rated d.c. voltage(Vcc).

If the intermediate d.c. voltage (Uz) is lower than the rated d.c.voltage (Vcc) (break contact element (Q) closed; relay (Re) off), theintermediate d.c. voltage (Uz) is, with the aid of a circuit of a seriesinduction coil (L) and switching controller (Ic2), controllably andupwardly transformed. The inductive voltage pulses arising from theinductive coil (L) are rectified with the aid of a second rectifiercircuit of a diode (D3) and smoothing capacitor (C3) and passed in theform of a positive rated d.c. voltage (Vcc+) to the output. By way ofexample, a circuit of the type Sl 17661 can be considered as anintegrated switching controller (Ic2). The third resistor (R3) isnecessary for the operation of the switching controller (Ic2). Theoutput voltage is tapped off for control purposes via an adjustablevoltage divider comprised of a fourth resistor (R4) and a potentiometer(P).

The upward transformation of the voltage with the aid of (L) and theswitching controller (Ic2) is necessary in portable machines such aschain saws or the like, especially at the starting up moment of theinternal combustion engine. The starting speed in such machines amountsto approximately 1000 revs/min which normally provides adequateelectrical power for heating the gripping handle of the chain saw orother implement. However, the voltage generated in the process isapproximately 80% lower than the requisite operating voltage (rated d.c.voltage) as is required e.g. for an injection valve. The directlyrectified and smoothed intermediate d.c. voltage (Uz) is supplied viathe break contact element (Q) to the switching controller (Ic2) directlywhich increases the voltage via the inductive coil (L). The inductancevoltage thusly obtained reaches the level of the necessary rated d.c.voltage.

If, when higher speeds are involved, the intermediate d.c. voltage (Uz)reaches the value of the rated d.c. voltage (Vcc), the switchingcontroller (Ic2) is switched off and the intermediate d.c. voltage (Uz)passes the switching controller (Ic2) only via the inductive coil (L)and the diode (D3). At the same time, as described already in theforegoing, the break contact element (Q) is opened and regulation by thevoltage controller (Ic1) reduces an increasing intermediate d.c. voltage(Uz) to the rated d.c. voltage (Vcc). Finally, in order to makeavailable the negative nominal d.c. voltage (Vcc−) for the electronics,an integrated voltage supply circuit (Ic3) (e.g., of the type LT1073)with the capacitors (C4, C5) is provided, which operates to produce anoutput for the negative d.c. voltage (Vcc−).

In summary, the present invention provides the ability, especially withgas engine-powered portable machines such as chainsaws, to supplyrequired electrical power to the fitted electronics without boosterbatteries, especially in the starting phase of engine operation. Whilethe preferred embodiment of the present invention has been describedherein, it is understood and acknowledged that variation andmodification can be made without departing from the scope of thepresently claimed invention.

What is claimed is:
 1. A circuit arrangement for batteryless powersupply of an electronic control of a machine, with a rated DC voltage,driven by an internal combustion engine, the machine possessing an ACvoltage generator driven by the internal combustion engine whichdelivers a generated voltage dependent upon the revolutions per minuteof the internal combustion engine, the circuit arrangement comprising: afirst rectifier circuit for converting the generated voltage into anintermediate DC voltage; and a first control means coupled to an outputof the first rectifier circuit for generating the rated DC voltage fromthe intermediate DC voltage by means of controlled upwardly transformingthe intermediate DC voltage level to the rated DC voltage level when theintermediate DC voltage level is lower than the rated DC voltage level.2. A circuit arrangement as defined in claim 1, wherein the firstcontrol means includes a switching controller, a series inductance coilcommunicating with the switching controller, and a second rectifiercircuit coupled to an output of the series inductance coil.
 3. A circuitarrangement as defined in claim 2, wherein the second rectifier circuitincludes a diode and a smoothing capacitor.
 4. A circuit arrangement asdefined in claim 1, further including a voltage controller disposedbetween the first rectifier circuit and the first control means suchthat the voltage controller generates the rated DC voltage from theintermediate DC voltage when the intermediate DC voltage level is higherthan the rated DC voltage level.
 5. A circuit arrangement as defined inclaim 4, further including a second control means for providing a shuntpath in parallel with the voltage controller when the intermediate DCvoltage level is lower than the rated DC voltage level.
 6. A circuitarrangement as defined in claim 5, wherein the second control meansincludes a relay and a break contact element, the break contact elementbeing connected in parallel with the voltage controller, and the relaybeing acted upon by the intermediate DC voltage.
 7. A circuitarrangement as defined in claim 6, wherein the relay is disposed betweenthe voltage controller and the first control means.
 8. A circuitarrangement as defined in claim 1, further including second controlmeans for the generation of a negative rated DC voltage.